This invention relates to radar systems and in particular to MTI radars and to a method and means for providing frequency agile operation of MTI radars.
MTI radars are well known in the art and are described in many publications such as M. J. Skolnik's Introduction to Radar Systems, chapter 4, pp 113-163, published by McGraw-Hill, 1962.
Frequency agile radars are also well known in the art and descriptions and operating principles of such systems are equally well documented. For example, U.S. Pat. No. 4,071,844 entitled Frequency Control for Frequency Agile Pulse Radar, F. W. Hopwood et al, and U.S. Pat. No. 4,023,169 entitled Automatic Frequency Control Circuit for Frequency Agile Radar, E. J. Kolp et al are typical of such publications.
Conventional radar design concepts and practices allow a radar to either change transmitted frequency on a pulse to pulse basis or to obtain moving target indicator (MTI) ground clutter cancellation operation. The latter requires a series of fixed frequency pulses and thus frequency agility and MTI are generally assumed to be fundamentally incompatible. This incompatibility presents a fundamental problem in the design of radars with intrinsically good electronic countercountermeasure (ECCM) performance. A good ECCM radar must have good rejection of both noise jamming and of radar chaff. Frequency agility is a basic and powerful technique for obtaining noise jammer rejection. Good chaff rejection, on the other hand, requires good MTI performance.
To date there has been no satisfactory solution to reconcile the incompatible aspects of the two types of radar systems. Accordingly, there currently exists the need for a technique that will permit frequency agile operation of an MTI radar. The present invention is directed toward satisfying that need.